U.S. patent application number 15/973848 was filed with the patent office on 2018-11-15 for signal modification via phase or frequency shifting.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Alberto Rico Alvarino, Xiao Feng Wang.
Application Number | 20180332589 15/973848 |
Document ID | / |
Family ID | 64097580 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180332589 |
Kind Code |
A1 |
Wang; Xiao Feng ; et
al. |
November 15, 2018 |
SIGNAL MODIFICATION VIA PHASE OR FREQUENCY SHIFTING
Abstract
An example method of wireless communication includes applying,
by a first wireless communication device, a scrambling sequence
associated with a cell to a set of symbol groups in a repetition.
The method also includes transmitting, by the first wireless
communication device to a second wireless communication device
associated with the cell, the set of symbol groups after the
scrambling sequence is applied to the set of symbol groups. Another
example method of wireless communication includes applying, by a
first wireless communication device, a frequency shift associated
with a cell to a set of symbol groups in a repetition. The method
also includes transmitting, by the first wireless communication
device to a second wireless communication device associated with
the cell, the set of symbol groups after the frequency shift is
applied to the set of symbol groups.
Inventors: |
Wang; Xiao Feng; (San Diego,
CA) ; Rico Alvarino; Alberto; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
64097580 |
Appl. No.: |
15/973848 |
Filed: |
May 8, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62504451 |
May 10, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0064 20130101;
H04L 5/0053 20130101; H04L 1/08 20130101; H04W 72/082 20130101;
H04W 74/0833 20130101; H04W 72/0466 20130101; H04L 25/03866
20130101; H04L 25/00 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04W 74/08 20060101 H04W074/08; H04W 72/08 20060101
H04W072/08 |
Claims
1. A method of wireless communication, comprising: applying, by a
first wireless communication device, a scrambling sequence
associated with a cell to a set of symbol groups in a repetition;
and transmitting, by the first wireless communication device to a
second wireless communication device associated with the cell, the
set of symbol groups after the applying the scrambling sequence to
the set of symbol groups.
2. The method of claim 1, wherein the set of symbol groups includes
four symbol groups.
3. The method of claim 1, wherein the scrambling sequence is cell
dependent.
4. The method of claim 3, wherein different repetitions in the cell
have a same predefined scrambling sequence or have different
predefined scrambling sequences.
5. The method of claim 1, wherein the scrambling sequence includes
entries of a constant absolute value.
6. The method of claim 1, wherein the applying the scrambling
sequence results in a magnitude of the set of symbol groups
remaining the same.
7. The method of claim 1, wherein the applying the scrambling
sequence includes applying a phase shift to one or more symbol
groups of the set of symbol groups.
8. The method of claim 1, wherein the scrambling sequence has four
defined values.
9. The method of claim 1, further comprising: receiving, by the
first wireless communication device, a cell ID of the cell; and
determining, by the first wireless communication device, the
scrambling sequence based on the cell ID.
10. The method of claim 9, wherein the scrambling sequence defines
a set of values.
11. The method of claim 10, wherein the applying the scrambling
sequence includes rotating a first symbol group of the set of
symbol groups by a first value listed in the set of values.
12. The method of claim 11, wherein the applying the scrambling
sequence includes rotating a second symbol group of the set of
symbol groups by a second value listed in the set of values.
13. The method of claim 1, comprising: applying, by the first
wireless communication device, a frequency shift associated with
the cell to the set of symbol groups in the repetition, wherein the
transmitting includes transmitting the set of symbol groups after
the applying the frequency shift.
14. The method of claim 1, wherein different cells use different
scrambling sequences.
15. The method of claim 1, wherein each symbol group includes a
group of symbols, each symbol being a single tone transmission.
16. A system for wireless communication, comprising: a scrambler
that applies a scrambling sequence associated with a cell to a set
of symbol groups in a repetition; and a transceiver that transmits
to a first wireless communication device associated with the cell,
the set of symbol groups after the scrambling sequence is applied
to the set of symbol groups.
17. The system of claim 16, further comprising: a second wireless
communication device that includes the scrambler and the
transceiver.
18. An apparatus for wireless communication, comprising: means for
applying a scrambling sequence associated with a cell to a set of
symbol groups in a repetition; and means for transmitting the set
of symbol groups after the scrambling sequence is applied to the
set of symbol groups.
19. A computer-readable medium having program code recorded
thereon, the program code comprising: code for causing a first
wireless communication device, to apply a scrambling sequence
associated with a cell to a set of symbol groups in a repetition;
and code for causing the first wireless communication device, to
transmit to a second wireless communication device associated with
the cell, the set of symbol groups after the scrambling sequence is
applied to the set of symbol groups.
20. A method of wireless communication, comprising: applying, by a
first wireless communication device, a frequency shift associated
with a cell to a set of symbol groups in a repetition; and
transmitting, by the first wireless communication device to a
second wireless communication device associated with the cell, the
set of symbol groups after the frequency shift is applied to the
set of symbol groups.
21. The method of claim 20, further comprising: applying, by the
first wireless communication device, a scrambling sequence
associated with the cell to the set of symbol groups in the
repetition, wherein the transmitting further includes transmitting
to the second wireless communication device the set of symbol
groups after the applying the scrambling sequence to the set of
symbols.
22. A system for wireless communication, comprising: a frequency
shifter that applies a frequency shift associated with a cell to a
set of symbol groups in a repetition; and a transceiver that
transmits to a first wireless communication device associated with
the cell, the set of symbol groups after the frequency shift is
applied to the set of symbol groups.
23. The system of claim 22, wherein an NPRACH signal includes the
set of symbol groups.
24. The system of claim 23, further comprising: a second wireless
communication device including the frequency shifter and the
transceiver.
25. An apparatus for wireless communication, comprising: means for
applying a frequency shift associated with a cell to a set of
symbol groups in a repetition; and means for transmitting to a
first wireless communication device associated with the cell, the
set of symbol groups after the frequency shift is applied to the
set of symbol groups.
26. A computer-readable medium having program code recorded
thereon, the program code comprising: code for causing a first
wireless communication device, to apply a frequency shift
associated with a cell to a set of symbol groups in a repetition;
and code for causing the first wireless communication device to
transmit to a second wireless communication device associated with
the cell, the set of symbol groups after the frequency shift is
applied to the set of symbol groups.
27. A method of wireless communication, comprising: detecting one
or more phase shifts between symbol groups; determining whether the
difference of two or more phase shifts match a set of expected
phase shift values associated with a cell; in response to a
determination that the difference of two or more phase shifts match
the set of expected phase shift values, detecting a signal
including the symbol groups; and in response to a determination
that the difference of two or more phase shifts do not match the
set of expected phase shift values, ignoring the signal including
the symbol groups.
28. A method of wireless communication, comprising: detecting
frequency shifts between symbol groups; determining whether the
difference of two or more frequency shifts match a set of expected
frequency shift values associated with a cell; in response to a
determination that the difference of two or more frequency shifts
match a set of expected frequency shift values, detecting a signal
including the symbol groups; and in response to a determination
that the difference of two or more detected frequency shifts do not
match the set of expected frequency shift values, ignoring the
signal including the symbol groups.
Description
CROSS REFERENCE TO RELATED APPLICATIONS & PRIORITY CLAIM
[0001] The present application claims priority to and the benefit
of the U.S. Provisional Patent Application No. 62/504,451 filed May
10, 2017, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] This application relates to wireless communication systems,
and more particularly to reducing cell interference by modifying a
signal via phase or frequency shifting.
INTRODUCTION
[0003] A wireless communication network may include a number of
base stations (BSs) that can support communication for a number of
user equipments (UEs). In recent years, the developments of
electronic, information, sensing, and application technologies
cause the Internet to evolve from a human-oriented network, where a
person creates and consumes information, into Internet of Things
(IoT), where distributed elements exchange and process information.
Thus, the demand for serving IoT type wireless data traffic is
increasing. For example, smart wireless meters and wireless sensors
may be installed throughout buildings in various areas. The smart
meters may send meter readings to utilities at some time periods,
for example, hourly, daily, or weekly. The sensors may send sensing
measurements to servers at some time periods, which may be based on
sensing events. IoT application packets are typically small in
size, for example, in tens of bytes to about 100 bytes.
[0004] Narrowband IoT (NB-IoT) is an emerging cellular technology
that provides coverage for a large number of low-throughput
low-cost devices with low device power consumption in
delay-tolerant applications. A new single tone signal with
frequency hopping has been designed for NB-IoT physical random
access channel (NPRACH).
BRIEF SUMMARY OF SOME EXAMPLES
[0005] The following summarizes some aspects of the present
disclosure to provide a basic understanding of the discussed
technology. This summary is not an extensive overview of all
contemplated features of the disclosure, and is intended neither to
identify key or critical elements of all aspects of the disclosure
nor to delineate the scope of any or all aspects of the disclosure.
Its sole purpose is to present some concepts of one or more aspects
of the disclosure in summary form as a prelude to the more detailed
description that is presented later.
[0006] For example, in an aspect of the disclosure a method of
wireless communication includes applying, by a first wireless
communication device, a scrambling sequence associated with a cell
to a set of symbol groups in a repetition. The method also includes
transmitting, by the first wireless communication device to a
second wireless communication device associated with the cell, the
set of symbol groups after the applying the scrambling sequence to
the set of symbol groups.
[0007] A system for wireless communication includes a scrambler
that applies a scrambling sequence associated with a cell to a set
of symbol groups in a repetition. The system also includes a
transceiver that transmits to a first wireless communication device
associated with the cell, the set of symbol groups after the
scrambling sequence is applied to the set of symbol groups.
[0008] In an additional aspect of the disclosure, an apparatus for
wireless communication includes means for means for applying a
scrambling sequence associated with a cell to a set of symbol
groups in a repetition. The apparatus also includes means for
transmitting the set of symbol groups after the scrambling sequence
is applied to the set of symbol groups.
[0009] In an additional aspect of the disclosure, a
computer-readable medium having program code recorded thereon, the
program code includes code for causing a first wireless
communication device, to apply a scrambling sequence associated
with a cell to a set of symbol groups in a repetition, and code for
causing the first wireless communication device, to transmit to a
second wireless communication device associated with the cell, the
set of symbol groups after the scrambling sequence is applied to
the set of symbol groups.
[0010] In an additional aspect of the disclosure, a method of
wireless communication includes applying, by a first wireless
communication device, a frequency shift associated with a cell to a
set of symbol groups in a repetition. The method also includes
transmitting, by the first wireless communication device to a
second wireless communication device associated with the cell, the
set of symbol groups after the frequency shift is applied to the
set of symbol groups.
[0011] In an additional aspect of the disclosure, a system for
wireless communication includes a frequency shifter that applies a
frequency shift associated with a cell to a set of symbol groups in
a repetition. The system also includes a transceiver that transmits
to a first wireless communication device associated with the cell,
the set of symbol groups after the frequency shift is applied to
the set of symbol groups.
[0012] In an additional aspect of the disclosure, an apparatus for
wireless communication includes means for applying a frequency
shift associated with a cell to a set of symbol groups in a
repetition. The apparatus also includes means for transmitting to a
first wireless communication device associated with the cell, the
set of symbol groups after the applying the frequency shift.
[0013] In an additional aspect of the disclosure, a
computer-readable medium having program code recorded thereon, the
program code includes code for causing a first wireless
communication device, to apply a frequency shift associated with a
cell to a set of symbol groups in a repetition, and code for
causing the first wireless communication device to transmit to a
second wireless communication device associated with the cell, the
set of symbol groups after the frequency shift is applied to the
set of symbol groups.
[0014] In an additional aspect of the disclosure, a method of
wireless communication includes detecting phase shifts between
symbol groups. The method also includes determining whether the
difference of two or more phase shifts match a set of expected
phase shift values. The method further includes in response to a
determination that the difference between one or more phase shifts
match a set of expected phase shift values, detecting a signal
including the symbol groups. The method also includes in response
to a determination that the one or more phase shifts do not match
the set of expected phase shift values, ignoring the signal
including the symbol groups.
[0015] In an additional aspect of the disclosure, a method of
wireless communication includes detecting frequency shifts between
symbol groups. The method also includes determining whether the
difference of two or more frequency shifts match a set of expected
frequency shift values. The method further includes in response to
a determination that the difference of two or more frequency shifts
match a set of expected frequency shift values, detecting a signal
including the symbol groups. The method also includes in response
to a determination that the one or more frequency shifts do not
match the set of expected frequency shift values, ignoring the
signal including the symbol groups.
[0016] Other aspects, features, and embodiments of the present
invention will become apparent to those of ordinary skill in the
art, upon reviewing the following description of specific,
exemplary embodiments of the present invention in conjunction with
the accompanying figures. While features of the present invention
may be discussed relative to certain embodiments and figures below,
all embodiments of the present invention can include one or more of
the advantageous features discussed herein. In other words, while
one or more embodiments may be discussed as having certain
advantageous features, one or more of such features may also be
used in accordance with the various embodiments of the invention
discussed herein. In similar fashion, while exemplary embodiments
may be discussed below as device, system, or method embodiments it
should be understood that such exemplary embodiments can be
implemented in various devices, systems, and methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates a wireless communication network
according to embodiments of the present disclosure.
[0018] FIG. 2 illustrates an NPRACH signal including four
repetitions.
[0019] FIG. 3 is a block diagram of an exemplary user equipment
(UE) that scrambles symbol groups included in a repetition
according to embodiments of the present disclosure.
[0020] FIG. 4 is a block diagram of an exemplary base station (BS)
that detects phase shifts in a signal according to embodiments of
the present disclosure.
[0021] FIG. 5 is a block diagram of an exemplary UE that applies
frequency shifting to a signal according to embodiments of the
present disclosure.
[0022] FIG. 6 is a diagram of a NPRACH signal with a frequency
shift-frequency grid according to embodiments of the present
disclosure.
[0023] FIG. 7 is a block diagram according to embodiments of the
present disclosure.
[0024] FIG. 8 is a block diagram of an exemplary BS that detects
frequency shifts in a signal according to embodiments of the
present disclosure.
[0025] FIG. 9 is a flow diagram of a method of modifying a signal
by scrambling a set of symbol groups according to embodiments of
the present disclosure.
[0026] FIG. 10 is a flow diagram of a method of modifying a signal
by applying one or more frequency shifts to a set of symbol groups
according to embodiments of the present disclosure.
DETAILED DESCRIPTION
[0027] The detailed description set forth below, in connection with
the appended drawings, is intended as a description of various
configurations and is not intended to represent the only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of the various
concepts. However, it will be apparent to those skilled in the art
that these concepts may be practiced without these specific
details. In some instances, well-known structures and components
are shown in block diagram form in order to avoid obscuring such
concepts.
[0028] The techniques described herein may be used for various
wireless communication networks such as code-division multiple
access (CDMA), time-division multiple access (TDMA),
frequency-division multiple access (FDMA), orthogonal
frequency-division multiple access (OFDMA), single-carrier FDMA
(SC-FDMA) and other networks. The terms "network" and "system" are
often used interchangeably. A CDMA network may implement a radio
technology such as Universal Terrestrial Radio Access (UTRA),
cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other
variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856
standards. A TDMA network may implement a radio technology such as
Global System for Mobile Communications (GSM). An OFDMA network may
implement a radio technology such as Evolved UTRA (E-UTRA), Ultra
Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),
IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of
Universal Mobile Telecommunication System (UMTS). 3GPP Long Term
Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS
that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are
described in documents from an organization named "3rd Generation
Partnership Project" (3GPP). CDMA2000 and UMB are described in
documents from an organization named "3rd Generation Partnership
Project 2" (3GPP2). The techniques described herein may be used for
the wireless networks and radio technologies mentioned above as
well as other wireless networks and radio technologies, such as a
next generation (e.g., 5.sup.th Generation (5G)) network.
[0029] FIG. 1 illustrates a wireless communication network 100
according to embodiments of the present disclosure. The network 100
may include a number of UEs 102 as well as a number of BSs 104. The
BSs 104 may include an Evolve Node B (eNodeB). A BS 104 may be a
station that communicates with the UEs 102 and may also be referred
to as a base transceiver station, a node B, an access point, and
the like.
[0030] The BSs 104 communicate with the UEs 102 as indicated by
communication signals 106. A UE 102 may communicate with the BS 104
via an uplink (UL) and a downlink (DL). The downlink (or forward
link) refers to the communication link from the BS 104 to the UE
102. The UL (or reverse link) refers to the communication link from
the UE 102 to the BS 104. The BSs 104 may also communicate with one
another, directly or indirectly, over wired and/or wireless
connections, as indicated by communication signals 108.
[0031] The UEs 102 may be dispersed throughout the network 100, as
shown, and each UE 102 may be stationary or mobile. The UE 102 may
also be referred to as a terminal, a mobile station, a subscriber
unit, etc. The UE 102 may be a cellular phone, a smartphone, a
personal digital assistant, a wireless modem, a laptop computer, a
tablet computer, etc. The network 100 is one example of a network
to which various aspects of the disclosure apply.
[0032] Each BS 104 may provide communication coverage for a
particular geographic area. In 3GPP, the term "cell" can refer to
this particular geographic coverage area of a BS and/or a BS
subsystem serving the coverage area, depending on the context in
which the term is used. In this regard, a BS 104 may provide
communication coverage for a macro cell, a pico cell, a femto cell,
and/or other types of cell. A macro cell generally covers a
relatively large geographic area (e.g., several kilometers in
radius) and may allow unrestricted access by UEs with service
subscriptions with the network provider. A pico cell may generally
cover a relatively smaller geographic area and may allow
unrestricted access by UEs with service subscriptions with the
network provider. A femto cell may also generally cover a
relatively small geographic area (e.g., a home) and, in addition to
unrestricted access, may also provide restricted access by UEs
having an association with the femto cell (e.g., UEs in a closed
subscriber group (CSG), UEs for users in the home, and the like). A
BS for a macro cell may be referred to as a macro BS. A BS for a
pico cell may be referred to as a pico BS. A BS for a femto cell
may be referred to as a femto BS or a home BS.
[0033] In the example shown in FIG. 1, the BSs 104a, 104b and 104c
are examples of macro BSs for the coverage areas 110a, 110b and
110c, respectively. The BSs 104d and 104e are examples of pico
and/or femto BSs for the coverage areas 110d and 110e,
respectively. As will be recognized, a BS 104 may support one or
multiple (e.g., two, three, four, and the like) cells.
[0034] The network 100 may also include relay stations. A relay
station is a station that receives a transmission of data and/or
other information from an upstream station (e.g., a BS, a UE, or
the like) and sends a transmission of the data and/or other
information to a downstream station (e.g., another UE, another BS,
or the like). A relay station may also be a UE that relays
transmissions for other UEs. A relay station may also be referred
to as a relay BS, a relay UE, a relay, and the like.
[0035] The network 100 may support synchronous or asynchronous
operation. For synchronous operation, the BSs 104 may have similar
frame timing, and transmissions from different BSs 104 may be
approximately aligned in time. For asynchronous operation, the BSs
104 may have different frame timing, and transmissions from
different BSs 104 may not be aligned in time.
[0036] In some implementations, the network 100 utilizes orthogonal
frequency division multiplexing (OFDM) on the downlink and
single-carrier frequency division multiplexing (SC-FDM) on the UL.
OFDM and SC-FDM partition the system bandwidth into multiple (K)
orthogonal subcarriers, which are also commonly referred to as
tones, bins, or the like. Each subcarrier may be modulated with
data. In general, modulation symbols are sent in the frequency
domain with OFDM and in the time domain with SC-FDM. The spacing
between adjacent subcarriers may be fixed, and the total number of
subcarriers (K) may be dependent on the system bandwidth. For
example, K may be equal to 72, 180, 300, 600, 900, and 1200 for a
corresponding system bandwidth of 1.4, 3, 5, 10, 15, or 20
megahertz (MHz), respectively. The system bandwidth may also be
partitioned into sub-bands. For example, a sub-band may cover 1.08
MHz, and there may be 1, 2, 4, 8 or 16 sub-bands for a
corresponding system bandwidth of 1.4, 3, 5, 10, 15, or 20 MHz,
respectively.
[0037] In an embodiment, the network 100 can be a LTE network.
Reference signals are pre-determined signals that facilitate the
communications between the BSs 104 and the UEs 102. For example, a
reference signal can have a particular pilot pattern or structure,
where pilot tones may span across an operational bandwidth or
frequency band, each positioned at a pre-defined time and a
pre-defined frequency. Control information may include resource
assignments and protocol controls. Data may include protocol data
and/or operational data.
[0038] In an embodiment, the UE 102 may contain a USIM (Universal
Subscriber Identity Module) that represents the International
Mobile Subscriber Identity (IMSI) and stores the corresponding
authentication credentials. This IMSI is used to identify an LTE
user (generally referred to as "subscriber" in 3GPP terminology)
uniquely. The USIM may participate in LTE subscriber authentication
protocol and generate cryptographic keys that form the basis for
the key hierarchy subsequently used to protect signaling and user
data communication between the UE 102 and BSs 104 over the radio
interface.
[0039] In an embodiment, the BSs 104 control one or more cells and
can broadcast system information associated with the network 100.
Some examples of system information may include physical layer
information such as cell bandwidths and frame configurations, cell
access information, cell identifier (ID), and neighbor cell
information. A UE 102 can access the network 100 by listening to
the broadcast system information and requests connection or channel
establishments with a BS 104. For example, the UE 102 can perform a
random access procedure to begin communication with the BS 104 and
subsequently may perform connection and/or registration procedures
to register with the BS 104. After completing the connection and/or
the registration, the UE 102 and the BS 104 can enter a normal
operation stage, where operational data may be exchanged. The BS
104 may assign a UE ID to the UE 102 for identifying the UE 102 in
the network 100. The data exchange between the BS 104 and the UE
102 during the normal operation may be based on the assigned UE
ID.
[0040] The UE 102 downloads the system information and uses the
system information to successfully communicate with the network. In
an embodiment, the BS 104 broadcasts system information, for
example, in the form of master information blocks (MIBs) and/or
system information blocks (SIBs). The system information may
include cell access related information, a channel configuration, a
physical random access (PRACH) configuration, cell ID, and/or
neighboring cell information. The UE 102 may receive the cell ID of
a particular cell via SIB messages or MIB messages.
[0041] NB-IoT may include one or more NPRACH signals. FIG. 2
illustrates an NPRACH signal including four repetitions 202. The
number of repetitions 202 may be configurable and depend on the
coverage level, the distance between the UE 102 and the cell, etc.
In FIG. 2, each repetition 202 includes four symbol groups 204, and
each symbol group 204 includes a cyclic prefix 206 and five
contiguous same-valued symbols at a given 3.75 kHz tone. Each
symbol group may be a NPRACH symbol group. The length of cyclic
prefix 206 may be 66.67 .mu.s for a cell radius up to 10 km and
266.67 .mu.s for a cell radius up to 40 km. In some embodiments,
each symbol group includes a group of symbols, each symbol being a
single tone transmission.
[0042] The NPRACH signal may repeat between each repetition 202,
and frequency hopping may occur between repetitions. NPRACH signals
associated with different cells may be differentiated by
cell-specific random hopping between repetitions. For a coverage
level with one repetition, a NPRACH signal received by cell A may
be exactly the same as a NPRACH signal received by cell B. The UE
102 may randomly hop between repetitions, and the random hopping
may be defined per cell. In this example, the UE 102 may provide
for cell-specific specific random hopping between repetitions. The
frequency hopping may be cell dependent in that the UE 102 may
apply a formula, which is a function of the cell ID, to determine
the frequency hopping. In an embodiment, the eNodeB may
differentiate one signal intended for one cell from another via the
hopping pattern because the eNodeB is self-aware of its own hopping
pattern.
[0043] In addition to frequency hopping between repetitions, the UE
104 may apply frequency hopping to symbol groups. In some
embodiments, the frequency hopping between symbol groups may be
defined in the specification and fixed for all of the cells. In
some embodiments, the frequency hopping between symbol groups may
be provided for in synchronization information. The tone frequency
index may change from one symbol group to another symbol group. For
example, the hop distance from symbol group 204a to symbol group
204b is 1 (may be +1 or -1), and associated with a frequency of
3.75 kHz. The hop distance from symbol group 204b to symbol group
204c is 6 (may be +6 or -6), associated with a frequency of
6.times.3.75 kHz. The hop distance from symbol group 204c to symbol
group 204d is 1 (may be +1 or -1), associated with a frequency of
3.75 kHz. The five symbols in symbol group 204 may be consistently
modulated by a constant value (e.g., 1). In some examples, the five
symbols represent a sinusoidal signal with the frequency being an
integer of a multiple of 0.75 kHz.
[0044] The positive or negative nature of the frequency hop
distance (e.g., +1, -1, +6, and -6) may depend on the starting tone
of the frequency location, which may be randomly chosen by the UE
102. If the hop distance from symbol group 204a to symbol group
204b is +1 and the hop distance from symbol group 204c to symbol
group 204d is +1, then the phase difference between symbol group
204a and symbol group 204b and the phase difference between symbol
group 204c and symbol group 204d should be exactly the same in the
absence of frequency offset because their distance in frequency
remains the same. If, however, the hop distance for symbol group
204a to symbol group 204b is +1 and the hop distance from symbol
group 204c to symbol group 204d is -1, then the phase difference
between symbol group 204a and symbol group 204b and the phase
difference between symbol group 204c and symbol group 204d should
be conjugate to each other. Similarly, if the hop distance for
symbol group 204a to symbol group 204b is -1 and the hop distance
from symbol group 204c to symbol group 204d is +1, then the phase
difference between symbol group 204a and symbol group 204b and the
phase difference between symbol group 204c and symbol group 204d
should also be conjugate to each other. Additionally, if the UE 102
applies a phase shift to symbol group 204d, then the previous cases
in which the phase differences are the same or conjugate to each
other will no longer hold.
[0045] Under the NPRACH design, the random access is the same for
all cells. The UE 102's random access to a cell, however, may have
some disadvantages. For example, the random access signal is the
same for all cells, and a cell may detect NPRACH signals intended
for another cell. NB-IoT covers a large geographical area, and the
NB-IoT NPRACH design may suffer from false alarms due to inter-cell
interference. For example, a cell A may suffer from interferences
from one or more random access intended for a cell B, which may be
referred to as a false alarm and may cause problems. Additionally,
the random access may cause inter-cell interference between cells A
and B. If cells A and B have NPRACH resources completely or
partially overlapped in time, a NPRACH signal intended for one cell
may be detected by another cell, particularly when the number of
repetitions is small. In addition, the timing estimation of a
random access of cell A may be biased due to interference from one
or more random access signals intended for other cells. It may be
desirable to reduce false alarms and/or inter-cell
interference.
[0046] Additionally, UEs may already be programmed to transmit
NPRACH signals in a particular way. The present disclosure provides
techniques for "new" UEs to modify NPRACH signals and transmit
these modified signals to cells such that the signals are not
detected by unintended cells. It may be desirable to provide these
new UEs with backward compatibility to communicate with components
in the network 100 and send the NPRACH signals disclosed in the
present disclosure.
[0047] FIG. 3 is a block diagram of an exemplary UE 300 that
scrambles a set of symbol groups included a repetition according to
embodiments of the present disclosure. The UE 300 may be a UE 102
as discussed above. As shown, the UE 300 may include a processor
302, a memory 304, a scrambler 308, a transceiver 310 including a
modem subsystem 312 and a RF unit 314, and an antenna 316. These
elements may be in direct or indirect communication with each
other, for example via one or more buses.
[0048] The processor 302 may include a central processing unit
(CPU), a digital signal processor (DSP), an application-specific
integrated circuit (ASIC), a controller, a field programmable gate
array (FPGA) device, another hardware device, a firmware device, or
any combination thereof configured to perform the operations
described herein. The processor 302 may also be implemented as a
combination of computing devices, e.g., a combination of a DSP and
a microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration.
[0049] The memory 304 may include a cache memory (e.g., a cache
memory of the processor 302), random access memory (RAM),
magnetoresistive RAM (MRAM), read-only memory (ROM), programmable
read-only memory (PROM), erasable programmable read only memory
(EPROM), electrically erasable programmable read only memory
(EEPROM), flash memory, solid state memory device, hard disk
drives, other forms of volatile and non-volatile memory, or a
combination of different types of memory. In an embodiment, the
memory 304 includes a non-transitory computer-readable medium. The
memory 304 may store instructions 306. The instructions 306 may
include instructions that, when executed by the processor 302,
cause the processor 302 to perform the operations described herein
with reference to the UEs in connection with embodiments of the
present disclosure. Instructions 306 may also be referred to as
code. The terms "instructions" and "code" should be interpreted
broadly to include any type of computer-readable statement(s). For
example, the terms "instructions" and "code" may refer to one or
more programs, routines, sub-routines, functions, procedures, etc.
"Instructions" and "code" may include a single computer-readable
statement or many computer-readable statements.
[0050] Additionally, the memory 304 may store a cell ID 311
received by the UE 300 and used by the UE 300 to apply the
techniques discussed in the present disclosure (e.g., to scramble
or frequency shift). The cell ID 311 may identify the cell with
which the UE 300 is connected and has been authenticated. The cell
may include its cell ID 311 in the synchronization information, and
the UE 300 may receive the synchronization information and store
the cell ID 311 into the memory 304.
[0051] The scrambler 308 may be used for various aspects of the
present disclosure. The scrambler 308 may reduce inter-cell
interference and the occurrence of false alarms. The scrambler 308
may apply a scrambling sequence at the symbol group level. For
example, the scrambler 308 may scramble a set of four symbol groups
204a, 204b, 204c, and 204d in the repetition 202d by a sequence of
length four. The scrambling may be done based on the cell ID
defined by the specification, or may be explicitly signaled in the
system information. The scrambler 308's use of a scrambling
sequence on the symbol groups may be cell specific. For example,
scrambler 308 may identify the scrambling sequence associated with
the cell ID 311, and apply that particular scrambler 308 sequence
to the set of symbol groups. The cell ID 311 may be associated with
the phase shift value 309, which provides information to the
scrambler 308 on the angle of the phase shift. If the UE 300
connects to another cell, the cell ID 311 may be updated to the new
cell's cell ID and the phase shift value 309 may be updated to
reflect the new cell's phase shift value. Different cells may use
different scrambling sequences. Additionally, different repetitions
in a cell may have the same or different scrambling sequences, and
different NPRACH resources may have different or the same
scrambling sequence. The scrambler 308 may apply different
scrambling sequences at the symbol group levels.
[0052] In some embodiments, the sequences that are applied are
associated with the network and the particular UE, and the
scrambler 308 applies different scrambling sequences among
different repetitions. The scrambling sequence may be dependent on
the cell (e.g., predefined based on the cell ID). After the cell is
defined, a particular scrambling sequence may be defined for all
the repetitions. In an example, four repetitions and four
scrambling sequences (e.g., 1, 2, 3, 4) are defined. For the cell
identified by the cell ID 311, the UE 300 may use sequence 1, 2, 3,
4 for repetitions 1, 2, 3, 4. In this example, for repetition 1,
the scrambler 308 may apply scrambling sequence 1 based on the cell
ID 311; for repetition 2, the scrambler 308 may apply scrambling
sequence 2 based on the cell ID 311, for repetition 3, the
scrambler 308 may apply scrambling sequence 3 based on the cell ID
311; and for repetition 4, the scrambler 308 may apply scrambling
sequence 4 based on the cell ID 311. For a second cell identified
by a second cell ID different from the cell ID 311, the UE 300 may
use the sequence 2, 3, 4, 1 for repetition 1, 2, 3, 4. In this
example, for repetition 1, the scrambler 308 may apply scrambling
sequence 2 based on the second cell ID; for repetition 2, the
scrambler 308 may apply scrambling sequence 3 based on the second
cell ID; for repetition 3, the scrambler 308 may apply scrambling
sequence 4 based on the second cell ID; and for repetition 4, the
scrambler 308 may apply scrambling sequence 1 based on the second
cell ID. In an example, all repetitions use the same sequence. For
example, the scrambler 308 may apply scrambling sequence 1, 1, 1, 1
for all 4 repetitions.
[0053] In some embodiments, a scrambling sequence includes entries
of a constant absolute value. In order to not change the signal
strength between symbol groups so that all four symbol groups have
the exact same strength. In this example, the magnitude remains the
same, and the scrambler 308 may apply a scrambling sequence by
applying a phase shift to one or more of the symbol groups, thus
changing the phase among one or more of the four symbol groups.
Although the disclosure may provide examples of the phase shifting
being applied to four symbol groups, it should be understood that
other examples provide for application of a scrambling sequence
being applied to more than or fewer than four symbol groups. The
term "phase rotation" and "phase shifting" may be used
interchangeably.
[0054] In some examples, the phase shift signal may be written in
exponential form as follows:
Signal=exp(j*s(n)), Equation (1)
[0055] where n=1, 2, 3, 4, s(n) represents the phase shift for
symbol group n, and j=square root of (-1). If the phase shift
s(n)=.pi./2, the scrambler 308 shifts or rotates the signal by this
phase shift value (e.g., .pi./2). In an example, the scrambler 308
may apply Equation (1) to the symbol group n and transmit this
signal to the BS 104. In some examples, scrambler 308 applies the
scrambling sequence to symbol groups 204a, 204b, 204c, and 204d by
rotating a symbol group 204a by a first value listed in the
scrambling sequence (e.g., 0), rotating symbol group 204b by a
second value listed in the scrambling sequence (e.g., .pi./2),
rotating symbol group 204c by a third value listed in the
scrambling sequence (e.g., .pi.), and rotating symbol group 204d by
a fourth value listed in the scrambling sequence (e.g.,
3.pi./2).
[0056] Equation (1) may be further simplified as shown in the
following Equation (2):
Phase rotation=s(n), Equation (2)
[0057] where n=1, 2, 3=0. In this example, s(n) has the value zero
for the first three symbols and thus the scrambler 308 does not
apply a phase rotation to symbol groups 1, 2, and 3 because they
are rotated by zero. The scrambler 308 may apply a phase shift
rotation to symbol group 4. For example, if s(n)=.pi./2, the
scrambling sequence may be in the form [0, 0, 0, .pi./2*.pi.], and
the scrambler 308 rotates the last symbol group 4 with possible
values [0, .pi./2, .pi., and 3.pi./2]. In an example, the scrambler
308 may apply a phase rotation given by Equation (2) to the symbol
group n and transmit this signal to the BS 104.
[0058] Application of the scrambling sequence may provide for a
robust scheme that provides for signal reuse. The robustness of the
scheme may depend on the phase shift of the angle. For example,
referring to Equation (2) with n=4, the distance is in the angle.
In an example, the four values [0, .pi./2, .pi. and 3.pi./2] are
defined for symbol group 4 and no phase shift for other symbol
groups, and the distance between each of the possible values is
.pi./2, which defines the robustness of the scheme. Cell A and
three other cells near cell A may use different defined values
relative to each other, due to their proximity The cells further
out, however, may reuse the value used by cell A. Additionally, if
the number of defined values goes beyond four, another scrambling
scheme may be provided.
[0059] The memory 304 may store one or more phase shift values 309,
which may provide the UE 300 with information on how much to shift
the phase of a signal (e.g., NPRACH signal). A phase shift value
309 may be provided in a variety of ways. In an example, the phase
rotation or phase shift value 309 is defined in the specification
as a function of the cell ID. In this example, four values may be
defined for the phase shift value 309. If the cell IDs have already
been assigned, it may be advantageous to provide a more flexible
avenue for the UE 300 to obtain the phase shift value 309 of a
cell. In another example, the cell provides its cell ID in
synchronization information. The synchronization information may
be, for example, a SIB message or MID message. The UE 300 may
synchronize with the cell and attach the synchronization
information (e.g., the SIB or MID information) to determine the
value of the phase shift value 309 (e.g., .pi./2). In some
examples, the phase shift value 309 is provided both in the
specification and also in the synchronization information. In an
example, the specification may define 32 values from 0 to 2.pi.,
and some phase shift values 309 are provided in the synchronization
information. Accordingly, the scrambler 308 may provide the UE 300
with a mechanism to reduce false alarms and inter-cell interference
within the network 100.
[0060] As shown, the transceiver 310 may include the modem
subsystem 312 and the RF unit 314. The transceiver 310 can be
configured to communicate bi-directionally with other devices, such
as the BSs 104. In some examples, the modem subsystem 312 may be
configured to communication with the scrambler 308 and modulate
and/or encode the data from the memory 304 according to the
scrambling scheme. The RF unit 314 may be configured to process
(e.g., perform analog to digital conversion or digital to analog
conversion, etc.) modulated/encoded data from the modem subsystem
312 (on outbound transmissions) or of transmissions originating
from another source such as a UE 102 or a BS 104. Although shown as
integrated together in transceiver 310, the modem subsystem 312 and
the RF unit 314 may be separate devices that are coupled together
at the UE 300 to enable the UE 300 to communicate with other
devices.
[0061] The RF unit 314 may provide the modulated and/or processed
data, e.g. data packets (or, more generally, data messages that may
contain one or more data packets and other information), to the
antenna 316 for transmission to one or more other devices. This may
include, for example, transmission of a random access preamble, a
connection request, or a NPRACH signal that has been modified by
scrambler 308 according to embodiments of the present disclosure.
The antenna 316 may further receive data messages transmitted from
other devices. The antenna 316 may provide the received data
messages for processing and/or demodulation at the transceiver 310.
Although FIG. 3 illustrates antenna 316 as a single antenna,
antenna 316 may include multiple antennas of similar or different
designs in order to sustain multiple transmission links. The RF
unit 314 may configure the antenna 316.
[0062] Using the scrambling sequence techniques provided in the
present disclosure, a cell may be better able to differentiate
between which signals are intended for it versus intended for
another cell. At the eNodeB, a manner of determining whether a
NPRACH signal is intended for another cell is to detect the phase
shifts between symbol groups (e.g., symbol groups 1 and 2, and
symbol groups 3 and 4) and determine whether this phase shift is
associated with (or assigned to) the cell. For example, cell A may
be identified by cell ID 311 and be associated with a phase shift
value 309 ".pi./2." If cell A determines that the difference
between symbol groups 204a and 204b is a degrees and the difference
between symbol groups 204c and 204d is close to .alpha.+.pi./2
degrees, cell A may determine that this received NPRACH signal is
intended for the cell. In this example, cell A is aware that the UE
102 rotates the last symbol group by a certain degree (e.g.,
.pi./2), and the symbol group is rotated or its phase is shifted as
cell A expects it to be. If, however, cell B is not associated with
a phase shift value of ".pi./2," this NPRACH signal is not intended
for cell B and cell B will not detect this NPRACH signal or discard
this repetition in timing estimation. In this example, cell B may
listen for signals that are associated with a phase shift value of
zero.
[0063] FIG. 4 is a block diagram of an exemplary BS 400 that
detects phase shifts in a signal according to embodiments of the
present disclosure. In an example, the signal is a NPRACH signal.
The BS 400 may be a BS 104 as discussed above. As shown, the BS 400
may include a processor 402, a memory 404, a transceiver 410
including a phase shift detector 411, modem subsystem 412 and a RF
unit 414, and an antenna 416. These elements may be in direct or
indirect communication with each other, for example via one or more
buses.
[0064] The processor 402 may have various features as a
specific-type processor. For example, these may include a CPU, a
DSP, an ASIC, a controller, a FPGA device, another hardware device,
a firmware device, or any combination thereof configured to perform
the operations described herein. The processor 402 may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0065] The memory 404 may include a cache memory (e.g., a cache
memory of the processor 402), RAM, MRAM, ROM, PROM, EPROM, EEPROM,
flash memory, a solid state memory device, one or more hard disk
drives, memristor-based arrays, other forms of volatile and
non-volatile memory, or a combination of different types of memory.
In some embodiments, the memory 404 may include a non-transitory
computer-readable medium. The memory 404 may store instructions
406. The instructions 406 may include instructions that, when
executed by the processor 402, cause the processor 402 to perform
operations described herein. Instructions 406 may also be referred
to as code, which may be interpreted broadly to include any type of
computer-readable statement(s) as discussed above with respect to
FIG. 3.
[0066] Additionally, the memory 404 may store one or more expected
phase shift value values 407 associated with (or assigned to) the
current cell and may further store the cell ID 311 of a cell to
which the UE 300 is connected. The current cell refers to the cell
with which the UE 300 is connected. The expected phase shift value
407 may be configurable. The cells adjacent to the current cell may
store different expected phase shift values than the current cell
in order to reduce confusion and inter-call interference. The
memory 404 may also store the cell's cell ID 311, which identifies
and provides information about the cell.
[0067] As shown, the transceiver 410 may include the phase shift
detector 411, the modem subsystem 412, and the RF unit 414. The
transceiver 410 can be configured to communicate bi-directionally
with other devices, such as the UEs 102 and 302 and/or another core
network element. The phase shift detector 411 may be used for
various aspects of the present disclosure. The phase shift detector
411 may reduce inter-cell interference and the occurrence of false
alarms. For example, the phase shift detector 411 may detect the
phase shifts between symbol groups and determine whether the
difference of these detected phase shifts are associated with or
match the one or more expected phase shift values 407. In an
example, phase shift detector 411 detect phase shifts between
symbol groups 204a and 204b and between symbol groups 204c and
204d, and determines whether the difference of these detected phase
shifts match an expected phase shift value. In response to a
determination that the one or more detected phase shifts match a
set of expected phase shift values, phase shift detector 411 may
detect a signal including the symbol groups. In this example, the
cell is the intended cell for the signal. In response to a
determination that the differences of one or more detected phase
shifts do not match the set of expected phase shift values, phase
shift detector 411 ignores the signal including the symbol groups.
In this example, the cell is not the intended cell for the
signal.
[0068] The modem subsystem 412 may be configured to modulate and/or
encode data. The RF unit 414 may be configured to process (e.g.,
perform analog to digital conversion or digital to analog
conversion, etc.) modulated/encoded data from the modem subsystem
412 (on outbound transmissions) or of transmissions originating
from another source such as a UE 102. Although shown as integrated
together in transceiver 410, the modem subsystem 412 and the RF
unit 414 may be separate devices that are coupled together at the
BS 104 to enable the BS 104 to communicate with other devices.
[0069] The RF unit 414 may provide the modulated and/or processed
data, e.g. data packets (or, more generally, data messages that may
contain one or more data packets and other information), to the
antenna 416 for transmission to one or more other devices (e.g.,
the UE 300). This may include, for example, transmission of
information to complete attachment to a network (e.g., cell ID)
according to embodiments of the present disclosure. The antenna 416
may further receive data messages transmitted from other devices
and provide the received data messages for processing and/or
demodulation at the transceiver 410. Although FIG. 4 illustrates
antenna 416 as a single antenna, antenna 416 may include multiple
antennas of similar or different designs in order to sustain
multiple transmission links.
[0070] FIG. 5 is a block diagram of an exemplary UE 500 that
applies frequency shifting to a signal according to embodiments of
the present disclosure. In an example, the signal is a NPRACH
signal. The UE 500 may be a UE 102 or UE 300 as discussed above. As
shown, the UE 500 may include a processor 302, a memory 504, a
frequency shifter 502, a transceiver 310 including a modem
subsystem 312 and a RF unit 314, and an antenna 316. These elements
may be in direct or indirect communication with each other, for
example via one or more buses. The memory 504 may store one or more
frequency shift values 504.
[0071] In some embodiments, the frequency shifter 502 applies one
or more frequency shifts to existing NPRACH signals before
transmitting them to BS 104. In an example, each symbol group 204
is a signal of an integer multiple of 0.75 kHz, and two NPRACH
signals allocated at tone k with frequency shifts of m1*0.75 kHz
and m2*0.75 kHz are orthogonal to each other. In this example,
there are five possible frequency shift values so that NPRACH
signals with different shift values are mutually orthogonal to each
other. The five possible shift values may be [-2, -1, 0, 1, 2]*0.75
kHz, which correspond to tone locations in FIG. 6.
[0072] FIG. 6 is a diagram of a NPRACH signal with a frequency
shift-frequency grid according to embodiments of the present
disclosure. In FIG. 6, the X-axis represents the frequency. The
NPRACH tone locations 602, 604, and 606 may represent the current
specification, or what is currently available. For each symbol
group, the UE 500 may select one of tone locations 602, 604, and
606 at a specified frequency, and sends five symbols of them. The
transmitted signal is the duration of that signal, which is one
period of 0.75 kHz. The new NPRACH tone locations 604, 608, 610,
612, and 614 may represent the new NPRACH tone locations that are
added. Each of the new NPRACH tone locations is 0.75 kHz apart from
each other, and the NPRACH tone locations 602, 604, and 606 and the
new NPRACH tone locations 604, 608, 610, 612, and 614 are frequency
locations. The tone locations may represent frequency locations and
are based on the specification, which provides a five symbol
duration of 3.75 kHz; these signals will be orthogonal to each
other.
[0073] In an example, if the UE 500 desires to send a symbol group
using the new NPRACH tone location 604, the UE 500 may shift the
signal to the right by 0.75 kHz, resulting in this signal being
orthogonal to any signals sent using the other tone locations. For
a cell B, the frequency shifter 502 may then use the new NPRACH
tone location 612, which is located to the right of the NPRACH tone
location 604. Additionally, for another cell C, the frequency
shifter 502 may use another tone location. For each of the NPRACH
tone locations 602, 604, and 606, five more new NPRACH tone
locations at 3.75 kHz/5=0.75 kHz may be provided. Although the new
NPRACH tone locations 604, 608, 610, 612, and 614 are plotted
around the initial NPRACH tone locations, this is not intended to
be limiting, and may be plotted in accordance with other
factors.
[0074] Existing UEs may have a frequency shift value 504 of zero
regardless of its intended cells. This zero value corresponds to
the current frequency location, and the existing UEs may be unable
to understand anything else in terms of the frequency shift value
504. In an example of backwards compatibility, the new UEs 500 may
use one of the five defined frequency shift values fd1=[-2, -1, 0,
1, 2]*0.75 kHz or zero (because the old UEs may use zero). In
another example, the new UEs 500 may use one of the four defined
frequency shift values fd2=[-2, -1, 1, 2]*0.75 kHz, which can be
assigned to a cell depending on its cell ID. For instance, entry
mod(cell_ID,5)+1 of fd1 or entry mod(cell_ID,4)+1 of fd2 may be
used, which may allow for a frequency reuse factor of 5 or 4, i.e.,
5 or 4 cells can have different frequency for NPRACH.
[0075] If two cells are assigned different frequency shift values,
the NPRACH signals of these two cells may be orthogonal to each
other, depending on how they overlap or collide in time. For
example, a NPRACH resource of cell A may exactly coincide with
NPRACH resource of cell B in both frequency and time, but this may
represent the worst case. In this example, the NPRACH resource
happens at the same time and same frequency location. If this is
the case, frequency shifter 502 may apply the frequency shifting
and if the two cells have different frequency shift values, they
will be orthogonal to each other. Accordingly, this may reduce the
inter-cell interference. If NPRACH resource of cell A and cell B
partially overlap in time, this may not cause a huge concern.
Although the signals will not be exactly orthogonal, the
interference may be small because the signals will be associated
with different frequency locations and they overlap only partially
in time.
[0076] The frequency shift value 504 may be provided in a variety
of ways. In an example, the frequency shift value 504 is defined in
the specification as a function of the cell ID and may thus be
fixed based on the cell ID. In this example, it may be desirable
for operators to consider this formula when assigning cell IDs to
allow efficient use of these frequency shifting techniques. In
another example, the frequency shift value 504 is provided in the
synchronization information.
[0077] Although the disclosure may discuss NB-IoTs, the disclosure
is not so limited. In general, assuming that the hopping distance
is an integer multiple of FH Hz, which is a value, and M symbols
(each having a duration of 1/FH) per symbol group (a contiguous
transmission without frequency change), M shifts can be created
with frequency shifts m*FH/M Hz, where m=0, . . . M-1.
[0078] FIG. 7 is a block diagram 700 according to embodiments of
the present disclosure. FIG. 7 includes an existing NPRACH signal
generator 702 and a frequency shifter 704, which may correspond to
frequency shifter 502. The existing NPRACH signal generator 702 may
be incorporated into the UE 500 and may generate NPRACH signals in
accordance with the NPRACH tone locations 602, 604, and 606. The
frequency shifter 704 may take as input the cell ID 706 of a cell
and one or more NPRACH tone locations 602, 604, and 606, and apply
frequency shifting accordingly. Afterward, frequency shifter 704
may transmit the resulting NPRACH signal to, for example, BS 104.
The resulting NPRACH signal may have a frequency of, for example,
the new NPRACH tone location 612 in shown in FIG. 6.
[0079] FIG. 8 is a block diagram of an exemplary BS 800 that
detects frequency shifts in a signal according to embodiments of
the present disclosure. The BS 800 may be a BS 104 as discussed
above. As shown, the BS 800 may include a processor 402, a memory
804, a transceiver 810 including a frequency shift detector 802,
modem subsystem 412 and a RF unit 414, and an antenna 416. These
elements may be in direct or indirect communication with each
other, for example via one or more buses.
[0080] Additionally, the memory 804 includes an expected frequency
shift value 804 and the cell ID 511 of a cell to which the UE 700
is connected. The frequency shift detector 802 may be used for
various aspects of the present disclosure. For example, the
frequency shift detector 802 detects the frequency shifts between
symbol groups and determines whether the difference of these
detected frequency shifts are associated with or match the expected
frequency shift value 804. In an example, the frequency shifter 502
detects frequency shifts between symbol groups and determines
whether the differences of two or more detected frequency shifts
match a set of expected frequency shift values. In response to a
determination that the one or more detected frequency shifts match
a set of expected frequency shift values, the frequency shifter 502
detects a signal including the symbol groups. In response to a
determination that the differences of two or more detected
frequency shifts do not match the set of expected frequency shift
values, the frequency shifter 502 ignores the signal including the
symbol groups.
[0081] It should be understood that although the UE 300 is
illustrated as including scrambler 308 and phase shift value 309,
the UE 300 may also include other components. For example, in some
embodiments, the UE 300 also includes the frequency shifter 502 and
one or more frequency shift values 504. In some embodiments, the BS
400 also includes the frequency shift detector 802, the one or more
expected frequency shift values 804, and the cell ID 511. In some
embodiments, the immediate neighbor cells have different expected
frequency shift values, and second-tier neighbor cells have
different scrambling sequences.
[0082] FIG. 9 is a flow diagram of a method 900 of modifying a
signal by scrambling a set of symbol groups according to
embodiments of the present disclosure. Steps of the method 900 can
be executed by a computing device (e.g., a processor, processing
circuit, and/or other suitable component) of a wireless
communication device, such as the UEs 102, 300, and 500. The method
900 may employ similar mechanisms as described with respect to the
network 100. The method 900 can be better understood with reference
to FIG. 2. As illustrated, the method 900 includes a number of
enumerated steps, but embodiments of the method 900 may include
additional steps before, after, and in between the enumerated
steps. In some embodiments, one or more of the enumerated steps may
be omitted or performed in a different order.
[0083] At step 910, the method 900 includes applying, by a first
wireless communication device, a scrambling sequence associated
with a cell to a set of symbol groups in a repetition. At step 920,
the method 900 includes transmitting, by the first wireless
communication device to a second wireless communication device
associated with the cell, the set of symbol groups after the
scrambling sequence is applied to the set of symbol groups.
[0084] FIG. 10 is a flow diagram of a method 1000 of modifying a
signal by applying one or more frequency shifts to a set of symbol
groups according to embodiments of the present disclosure. Steps of
the method 1000 can be executed by a computing device (e.g., a
processor, processing circuit, and/or other suitable component) of
a wireless communication device, such as the UEs 102, 300, and/or
500. The method 1000 may employ similar mechanisms as described
with respect to the network 100. The method 1000 can be better
understood with reference to FIG. 2. As illustrated, the method
1000 includes a number of enumerated steps, but embodiments of the
method 1000 may include additional steps before, after, and in
between the enumerated steps. In some embodiments, one or more of
the enumerated steps may be omitted or performed in a different
order.
[0085] At step 1010, the method 1000 includes applying, by a first
wireless communication device, a frequency shift associated with a
cell to a set of symbol groups in a repetition. At step 1020, the
method 1000 includes transmitting, by the first wireless
communication device to a second wireless communication device
associated with the cell, the set of symbol groups after the
frequency shift is applied to the set of symbol groups.
[0086] The various illustrative blocks and modules described in
connection with the disclosure herein may be implemented or
performed with a general-purpose processor, a DSP, an ASIC, an FPGA
or other programmable logic device, discrete gate or transistor
logic, discrete hardware components, or any combination thereof
designed to perform the functions described herein. A
general-purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices (e.g., a
combination of a DSP and a microprocessor, multiple
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration).
[0087] The functions described herein may be implemented in
hardware, software executed by a processor, firmware, or any
combination thereof. If implemented in software executed by a
processor, the functions may be stored on or transmitted over as
one or more instructions or code on a computer-readable medium.
Other examples and implementations are within the scope of the
disclosure and appended claims. For example, due to the nature of
software, functions described above can be implemented using
software executed by a processor, hardware, firmware, hardwiring,
or combinations of any of these. Features implementing functions
may also be physically located at various positions, including
being distributed such that portions of functions are implemented
at different physical locations. Also, as used herein, including in
the claims, "or" as used in a list of items (for example, a list of
items prefaced by a phrase such as "at least one of" or "one or
more of") indicates an inclusive list such that, for example, a
list of [at least one of A, B, or C] means A or B or C or AB or AC
or BC or ABC (i.e., A and B and C).
[0088] As those of some skill in this art will by now appreciate
and depending on the particular application at hand, many
modifications, substitutions and variations can be made in and to
the materials, apparatus, configurations and methods of use of the
devices of the present disclosure without departing from the spirit
and scope thereof. In light of this, the scope of the present
disclosure should not be limited to that of the particular
embodiments illustrated and described herein, as they are merely by
way of some examples thereof, but rather, should be fully
commensurate with that of the claims appended hereafter and their
functional equivalents.
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